In Philadelphia, the express tracks on the Broad Street Line are most certainly used. Philly also has express trains (but not tracks) on the Market-Frankford El.

Budapest most certainly has the fastest escalators. Those things can give you whiplash.

DC needs to remove seats from the cars to allow for more standing. At least 3 days a week I have to let a train or two go by before I can get on.

Other cities besides Paris are developing those "never-ending" snaking cars. I think I've seen them in Prague and Vienna, (but maybe it was elsewhere in Europe?).

I would argue that Chicago has the loudest subway I've been on. You can hardly carry on a conversation on the Red Line.